feat(#1): Set up monorepo scaffold with pnpm workspaces + TurboRepo

Implements the foundational project structure including:
- pnpm workspaces configuration
- TurboRepo for build orchestration
- NestJS 11.1.12 API (apps/api)
- Next.js 16.1.6 web app (apps/web)
- Shared packages (config, shared, ui)
- TypeScript strict mode configuration
- ESLint + Prettier setup
- Vitest for unit testing (19 passing tests)

Fixes #1

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

turbo.json

@@ -0,0 +1,39 @@
+{
+  "$schema": "https://turbo.build/schema.json",
+  "tasks": {
+    "build": {
+      "dependsOn": ["^build"],
+      "outputs": ["dist/**", ".next/**", "!.next/cache/**"]
+    },
+    "dev": {
+      "cache": false,
+      "persistent": true
+    },
+    "lint": {
+      "dependsOn": ["^build"],
+      "outputs": []
+    },
+    "lint:fix": {
+      "outputs": []
+    },
+    "test": {
+      "dependsOn": ["^build"],
+      "outputs": ["coverage/**"]
+    },
+    "test:watch": {
+      "cache": false,
+      "persistent": true
+    },
+    "test:coverage": {
+      "dependsOn": ["^build"],
+      "outputs": ["coverage/**"]
+    },
+    "typecheck": {
+      "dependsOn": ["^build"],
+      "outputs": []
+    },
+    "clean": {
+      "cache": false
+    }
+  }
+}